This invention relates to medical treatments and composition and procedures useful therein. More specifically, it relates to cell-based gene transfer systems for administration to the pulmonary system of a mammalian patient.
Cell-based gene transfer is a known, albeit relatively new and experimental, technique for conducting gene therapy on a patient. In this procedure, DNA sequences containing the genes which it is desired to introduce into the patient""s body (the trans-gene) are prepared extracellularly, e.g. by using enzymatic cleavage and subsequent recombination of DNA from the patient""s cells with insert DNA sequences. Mammalian cells such as the patient""s own cells are then cultured in vitro and treated so as to take up the transgene in an expressible form. The trans-genes may be foreign to the mammalian cell, or additional copies of genes already present in the cell, to increase the amount of expression product of the gene. Then the cells containing the trans-gene are introduced into the patient, so that the gene may express the required gene products in the body, for therapeutic purposes. The take-up of the foreign gene by the cells in culture may be accomplished by genetic engineering techniques, e.g. by causing transfection of the cells with a virus containing the DNA of the gene to be transferred, by cell fusion with cells containing the required gene, by lipofection, by electroporation, or by other accepted means to obtain transfected cells.
This is sometimes followed by selective culturing of the cells which have successfully taken up the transgene in an expressible form, so that administration of the cells to the patient can be limited to the transfected cells expressing the trans-gene. In other cases, all of the cells subjected to the take-up process are administered.
This procedure has in the past required administration of the cells containing the trans-gene directly to the body organ requiring treatment with the expression product of the trans-gene. Thus, transfected cells in an appropriate medium have been directly injected into the liver or into the muscle requiring the treatment, to enter the systemic circulation of the organ requiring treatment.
Previous attempts to introduce such genetically modified cells into the systemic circulation of a patient have encountered a number of problems. For example, there is difficulty in ensuring a sufficiently high assimilation of the genetically modified cells by the specific organ or body part where the gene expression product is required for best therapeutic benefit. This lack of specificity leads to the administration of excessive amounts of the genetically modified cells, which is not only wasteful and expensive, but also increases risks of side effects. In addition, many of the transplanted genetically modified cells do not survive when administered to the systemic circulation, since they encounter relatively high arterial pressures. Infusion of particulate materials, including cells, to other systemic circulations such as the brain and the heart, may lead to adverse consequences, i.e. ischemia and even infarction.
It is an object of the present invention to provide a novel procedure of cell based gene transfer to mammals.
It is a further and more specific object of the invention to provide novel uses and novel means of administration of angiogenic factors in human patients.
The present invention is based upon the discovery that the pulmonary system of a mammal, including a human, offers a potentially attractive means of introducing genetically altered cells into the body, for purposes of gene therapy, i.e. cell based gene transfer. The pulmonary system has a number of unique features rendering it particularly suited to a cell-based gene transfer. Thus, low arterial pressure and high surface area with relatively low shear in the micro-circulation of the lungs increase the chances of survival of the transplanted cells. High oxygenation in the micro-circulation of the ventilated lung also improves the viability of the transplanted cells.
Moreover, the pulmonary circulation functions as a natural filter, and is able to retain the infused cells efficiently and effectively. This is in contra-distinction to other systemic circulations, such as the brain and the heart, where the infusion of particulate materials such as cells could lead to the aforementioned adverse consequences. The lung presents a massive vascular system. The high surface area of the pulmonary endothelium allows the migration of the transplanted cells trapped in the micro-circulation across the endothelial layer to take up residence within the perivascular space.
The pulmonary circulation, unlike any other circulation in the body, receives the entire output of the heart. Accordingly, it offers the greatest opportunity to release a gene product into the circulation. This distinct property of the lung is particularly useful for pulmonary gene therapy and for the treatment of a systemic, rather than a pulmonary disorder.
It is believed that the transfected cells become lodged in the small artery-capillary transition regions of the pulmonary circulation system, following simple intravenous injection of the transfected cells to the patient. Products administered intravenously by appropriate means move with the circulation to the lungs and then to the heart. The transfected cells administered according to the invention appear to lodge in the small artery-capillary transition regions of the circulatory system of the lungs, from where they deliver expression products of the trans-genes, initially to the lungs, making the process to the present invention especially applicable to treatment of pulmonary disorders, and thence to the general circulation for treatment of disorders of other body organs.
Thus, according to a first aspect of the present invention, there is provided a process of conducting gene therapy in a mammalian patient, which comprises administering to the pulmonary system of the patient, genetically modified cells containing an expressible trans-gene which is capable of expressing at least one gene product in the pulmonary circulation after administration thereto.
A second aspect of the present invention is the treatment of pulmonary hypertension (PH). Primary pulmonary hypertension (PPH) and other causes of PH are associated with severe abnormalities in endothelial function, which likely play a critical role in its pathogenesis. The vasodilatory, anti-thrombotic and anti-proliferative factor, nitric oxide (NO) has been demonstrated to decrease pulmonary pressures in both experimental and clinical situations. However, long-term viral-based methods may cause significant local inflammation. Other, previous attempts to treat PPH have involved the use of prostacyclin, using continuous administration, but this is a difficult and expensive procedure, liable to give rise to side effects.
The present invention provides, from this second aspect, a method of alleviating the symptoms of PPH (and other causes of PH) which comprises administering to the pulmonary system of a patient suffering therefrom, at least one vasoactive gene such as an angiogenic factor, or a precursor or genetic product capable of producing and releasing into the pulmonary circulation at least one angiogenic factor.
An embodiment of this second aspect of the present invention is the delivery to a patient suffering from PPH of genetically modified cells containing a gene capable of expressing in vivo at least one angiogenic factor, by a process of cell-based gene transfer as described above. This second aspect of invention, however, is not limited to any specific form of administration, but pertains generally to the use of angiogenic factors and precursors thereof which produce angiogenic factors in situ, in treating or alleviating the symptoms of PPH, delivered to the pulmonary circulation by any suitable means.
Specific examples of useful angiogenic factors in the present invention include; vascular endothelial growth factor (VEGF) in all of its various known forms, i.e. VEGF165 which is the commonest and is preferred for use herein, VEGF205, VEGF189 and VEGF121; fibroblast growth factor (FGF), angiopoietin-1, transforming growth factor -xcex2 (TGF-xcex2), and platelet derived growth factor (PDGF). Also useful is the aforementioned vasodilatory factor nitric oxide (NO). DNA sequences constituting the genes for these angiogenic factors are known, and they can be prepared by the standard methods of recombinant DNA technologies (for example enzymatic cleavage and recombination of DNA), and introduced into mammalian cells, in expressible form, by standard genetic engineering techniques such as those mentioned above (viral transfection, cell fusion, electroporation, lipofection, use of polycationic proteins, etc).
In addition, however, the angiogenic factors can be administered directly to the patient, e.g. by direct infusion of the angiogenic factor, into the vasculature intravenously. They can also be administered to the patient by processes of inhalation, whereby a replication-deficient recombinant virus coding for the angiogenic factor is introduced into the patient by inhalation in aerosol form, or by intravenous injection of the DNA constituting the gene for the angiogenic factor itself (although this is inefficient). Administration methods as used in known treatments of cystic fibrosis can be adopted.
Angiogenic factors such as those mentioned above have previously been proposed for use as therapeutic substances in treatment of vascular disease. It is not to be predicted from this work, however, that such angiogenic factors would also be useful in treatment of pulmonary hypertension. Whilst it is not intended that the scope of the present invention should be limited to any particular theory or mode of operation, it appears that angiogenic growth factors may also have properties in addition to their ability to induce new blood vessel formation. These other properties apparently include the ability to increase nitric oxide production and activity, and/or decrease the production of endothelin-1, in the pulmonary circulation, so as to improve the balance of pulmonary cell nitric oxide in endothelin-1 production.
In preparing cells for transformation and subsequent introduction into a patient""s pulmonary system, it is preferred to start with mammalian cells, obtained from the eventual recipient. Thus, somatic cells are harvested from the eventual recipient, e.g. by removal of a safenas vein and culture of either smooth muscle cells or endothelial cells, or the culture of cells from other readily available tissues including adicytes from subcutaneous fat biopsies or dermal fibroblasts, etc. The culture methods are standard culture techniques with special precautions for culturing of human cells with the intent of re-implantation.
The somatic gene transfer in vitro to the recipient cells, i.e. the genetic engineering, is performed by standard and commercially available approaches to achieve gene transfer, as outlined above. Preferably, the method includes the use of poly cationic proteins (SUPERFECT*) available commercially which enhances gene transfer. However, other methods such as lipofection, electroporation, viral methods of gene transfer including adeno and retro viruses, may be employed. These methods and techniques are well known to those skilled in the art, and are readily adapted for use in the process of the present invention.
The re-introduction of the genetically engineered cells into the pulmonary circulation can be accomplished by infusion of cells either into a peripheral vein or a central vein, from where they move with the circulation to the pulmonary system as previously described. The infusion can be done either in a bolus form i.e. injection of all the cells during a short period of time, or it may be accomplished by a continuous infusion of small numbers of cells over a long period of time, or alternatively by administration of limited size boluses on several occasions over a period of time.